4 Answers
4

No - even in Shul you only answer Amein if it is done immediately or else it is an Amein Yesoma. Therefore you should not answer Amein if you are listening to a pre recorded Shiur. However if you are listening to a live Shiur then I do not know whether you should answer or not.

Although if the shiur was live, it could be allowed (you don't need to hear the bracha to answer amein, like in the famous shul in Alexandria where they used to wave flags to tell people to answer Amein)

The Rivevos Ephraim 8:102:2 writes that watching the syium hashas (live)on tv and hears kaddish ,one can answer amen yehei shmei rabbah... Since it is not the shem Hashem,he also talks about hearing thunder over the phone and holds one may say bracha without Shem UMalchus.